Wireless communication networks are becoming increasingly popular due to recently improved wireless communication technologies that make wireless networks relatively inexpensive. For example, there are currently a large number of spread spectrum wireless transceivers available that use the industrial, scientific and medical (ISM) allocated frequency spectrum of 2.4-2.4835 GHz. These types of ISM frequency transceivers are used in applications such as computer Local Area Networks (LANs). Often these transceivers employ a frequency hopping spread spectrum (FHSS) protocol that serves to spread the transmitted signal over a predetermined bandwidth. The FHSS protocol is helpful for alleviating interference and increasing communication bandwidth over the limited frequency spectrum.
In a LAN, for example, reliable communication is considered important but not vital. Reliable communication is relatively easy to accomplish because of the almost ideal conditions associated with stationary transceivers since the transceivers are positioned in advance to avoid obstacles. Moreover, if a data error occurs, the LAN receiver can request data retransmission, where the only inconvenience is a time delay.
However, for a railroad control system, reliable communication is considered vital. When an ISM transceiver is positioned in a mobile station, such as a locomotive, reliable communication is difficult due to impairments such as Doppler shifts from the mobile station movement, specular multipath from signal reflections (from buildings or in tunnels), interference from other local signals such as microwave ovens and RF light bulbs, transmission delays, latencies and anomalous propagations properties of RF signals in a metropolitan environment. Moreover, in a wireless railroad yard configuration with moving locomotives, communication must be reliable in order to efficiently command the locomotives along the tracks and to prevent accidents. These impairments cannot be overcome with conventional radio technology in order to insure reliable communication.